1. Field of the Invention
This invention relates generally to wind-powered vehicles and more particularly to vehicles having wind-driven propellers rather than traditional sails.
2. Background Art
When two streams are moving at different speeds or in different directions, a velocity differential is said to exist between the streams. Velocity differentials are plentiful in nature. Wind blowing over stationary water creates an air/water velocity differential A river flowing beneath still air or air at a different speed or direction also creates an air/water differential. The wind atop a sail is blowing faster than wind near a boat""s deck, an air/air vertical velocity differential exists. If a river is flowing faster at its surface near the middle of the stream as compared to deeper water or water near shore, a water/water differential exists which may be tapped.
Consider a vehicle traveling at some speed and direction that is unrelated to the direction of the two streams. The present invention provides a means of extracting kinetic energy generated by the velocity differential and redirecting it to propel the vehicle. A part of the mechanism is anchored or in direct contact with each of the streams, and the extracted energy minus frictional losses is used to accelerate the vehicle and overcome drag. Excess kinetic energy can alternately be converted to electrical energy, which is storable in auxiliary batteries, fuel cells or other devices for use in motoring the vehicle under calm conditions.
It is possible for such a vehicle of efficient design to travel at high multiples of the velocity differential in any direction relative to the direction of either stream. For example, a sailboat employing a modestly efficient design would be able to sail in any direction including directly into the wind and directly downwind at 3 to 5 times wind speed. The same boat on a river is also be able to run at multiples of river speed upstream, downstream and across the stream. A land vehicle with an air propeller could be used for recreational purposes on a solid surface.
An energy recovery and redirection mechanism is made up of one or more independent pivoting blades (IPB) air propellers and/or one or more IPB water propellers whose rotations are all linked together to a common drive. The mechanism is designed to self-adjust continuously in response to changes in the direction and speed of all the streams relative to the vehicle""s speed and direction without manual intervention as is required in traditional sailboats.
Multiple patents describe devices having two propellers, one in contact with a water stream, and the other in contact with an air stream. In all cases, the pitch of at least one of the propellers must be manually adjusted to provide propulsion under varying wind conditions. Prior art taught in U.S. Pat. No. 4,371,346, to Vidal, describes a device requiring a minimum of four controls to operate. The first control is a steering device such as a rudder. The second, is means to position the air propeller so that it has a desired angular disposition relative to the wind. Lastly; means is provided to control independently two of the following three variables: the pitch of the air propeller, the pitch of the water propeller, or the gear ratio of a transmission that connects the two propellers. This design suffers from the following shortcomings:
The angular disposition of the air propeller relative to the wind must be continuously adjusted as the direction of the wind changes. This also requires deck space for the propeller to pivot 360 degrees about a supporting mast.
The propeller pitch and/or transmission ratio must be continually manually adjusted as the speed and direction of the air and wind streams change.
Since the pitches of all the blades change in unison, vertical components of stream energy cannot be used to provide propulsion, but rather impede progress.
Stream velocity gradients cannot be exploited to provide propulsion; forces in these gradients actually oppose one another instead of combining to extract maximum energy.
In accordance with the present invention, a wind-powered vehicle designed to travel across a generally horizontal relatively dense medium such as water, ice or land is provided. The vehicle includes a body having a longitudinal axis generally aligned with the vehicle""s direction of travel and extending within a vertically disposed plane. The vehicle further includes a propeller assembly rotatable about a propeller axis extending within the vertically disposed plane. The propeller assembly has at least two blades extending outward from the propeller axis and pivotally attached to a rotary hub that rotates about the propeller axis. The at least two blades each pivot about a blade pivot axis that is generally perpendicular to the propeller axis. The blades are biased by springs to an initial angular disposition about the blade pivot axis. Wind load caused by a wind moving relative to the vehicle and in a direction generally parallel to a horizontal plane causes each blade to rotate about its respective blade pivot axis until the torque loads on the blades caused by the wind and by the springs are balanced. The blades are thus efficiently positioned relative to the wind to cause the propeller assembly to rotate about the propeller axis.
The vehicle also has a rotary coupling having a first end driven by the rotary hub and a second end providing a rotary output spaced therefrom, and it has a rotary drive member driven and cooperating with the second end of the rotary coupling. The rotary drive member cooperates with a relatively dense medium to drive the vehicle body forward in response to rotation of the propeller assembly by a wind load.